1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a technique which can enhance a contrast of a reflective liquid crystal display device adopting an IPS system.
2. Description of the Related Art
With respect to a liquid crystal display device, a so-called transmissive liquid crystal display device which usually uses a backlight and controls light from the backlight using liquid crystal has been popularly used. On the other hand, with respect to a display device which is installed in a place where an external light always exists, with the use of a reflective liquid crystal display device which uses an external light, power necessary for the backlight can be saved. In using a mobile phone or the like outside, there may be a case that the transmissive liquid crystal display device mounted on the mobile phone or the like cannot acquire a sufficient contrast due to a strong external light. Accordingly, when the mobile phone or the like is used outside, there also has been a strong demand for the use of the reflective liquid crystal display device.
In the liquid crystal display device, liquid crystal is sandwiched between a color filter substrate on which color filters and the like are formed and a TFT substrate on which pixel electrodes, TFTs (thin film transistors) and the like are formed. Here, with respect to the reflective liquid crystal display device, reflective electrodes having unevenness which reflect an external light are formed on the TFT substrate and an image is formed by controlling the reflection light.
JP-A-2002-162646 (patent document 1) discloses a technique which simplifies a manufacturing process of the reflective liquid crystal display device by using a photoresist as a background insulation film for forming the unevenness on the reflective electrodes thus enhancing productivity. JP-A-11-305221 (patent document 2) discloses a technique which forms pixel electrodes as reflective electrodes and applies an insulation film to the pixel electrodes by coating for preventing lowering of contrast attributed to a fluctuation of a cell gap of a liquid crystal layer when unevenness is formed on the pixel electrodes, and a surface of the insulation film is leveled by chemical-mechanical polishing (CMP).